Which method is least affected by hemolysis?

The Biuret method is the correct choice because it measures the concentration of proteins in a sample based on the formation of a colored complex when copper ions bind to peptide bonds under alkaline conditions. This method is relatively robust against interference from hemolysis because hemolysis primarily releases hemoglobin and other intracellular components from red blood cells into the serum, which can affect some protein measurement methods. However, in the case of the Biuret method, the presence of hemoglobin does not significantly interfere with the reaction that forms the color complex used for measurement.

Moreover, hemolysis typically leads to an increase in free hemoglobin levels, but since the Biuret method reacts specifically with peptide bonds and not with free hemoglobin, the impact on the results is minimal compared to other methods. On the other hand, methods like the Folin-Lowry and Kjeldahl’s procedure can be considerably influenced by the presence of hemolysate, as free hemoglobin and other components might alter the reaction dynamics or absorbance readings. Refractometry, which measures the refractive index of a solution, may also be affected by the turbid or cloudy appearance from hemolysis, leading to inaccuracies.

Therefore, the Biuret method stands out as the choice that